net/guacamole-server: Use upstream release archive and fix build with FFmpeg 6.0

Use upstream release archive as recommended by Porters Handbook
Backport upstream commit 5cf408ebbba9544fb5dfb297d98d5a1e1751a56d to
fix build with FFmpeg 6.0

References:
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=261302#c46
https://github.com/apache/guacamole-server/commit/5cf408ebbba9544fb5dfb297d98d5a1e1751a56d.patch

PR: 270313
Reported by: antoine (via exp-run)
Reviewed by: ultima (maintainer)